The most common type of gear is the spur gear. These gears have straight teeth and must be mounted on parallel shafts for their teeth to mesh with those of other gears. The disadvantage of spur gears is that they make a lot of noise when they are used at high speeds, and their design puts lots of stress on the gear teeth. For this reason spur gears are known as slow speed gears. The noise of spur gears can be reduced by precision gear grinding.

Spur gears can be used to increase or decrease the torque, or power, of a given object especially if the design will not allow for a side load on the support bearings. Spur gears are used to this effect in, washing machines, blenders, clothes dryers, construction equipment, mills and pumps for fuel, lubricating oil and most fluids. In power stations, so-called 'trains' of spur gears are used to convert a form of energy, such as wind or hydroelectric power, into electrical energy. Spur gears are also used in off shore winches and slewing rings on jib cranes on off shore oil rigs.